Electrode arrangement for direct current fed gas discharge lamps

ABSTRACT

A d.c. gas discharge lamp in which the space at the electrodes communicates through one or more apertures sufficiently small in cross-section to prevent arcing but sufficiently large to permit diffusion of metallic vapor. A single channel or a diaphragm may be utilized in a hot or cold cathode tube.

United States Patent Walz [ 51 Sept. 5, 1972 [54] ELECTRODE ARRANGEMENT FOR Primary Examiner-Roy Lake DIRECT CURRENT FED GAS Attorney-Bums, Doane, Swecker & Mathis DISCHARGE LAMPS ABSTRACT [72] Inventor: Alfred Walz, Am Kurzarm 7, Em-

- mendingen/Baden, Germany A d.c. gas discharge lamp in which the space at the electrodes communicates through one or more aper- [22] Filed: 20, 1970 tures sufficiently small in cross-section to prevent arc-. 21 A 1. N I 82 435 ing but sufficiently large to permit diffusion of metallic 1 pp 0 vapor. A single channel or a diaphragm may be nul- 52 US. Cl ..313/220 ized in e hate l m??? tube- [51] Int. Cl ..H0lj 17/16 [58] Field of Search ..3l3/220 [56] References Cited 2 UNITED STATES PATENTS 3,117,248 l/l964 Lake ..3l3/220 X {20 19 l0 l2 f X Z Y 6 (III! 1 III/II I3 L I 2| l a I8 ELECTRODE ARRANGEMENT FOR DIRECT CURRENT FED GAS DISCHARGE LAMPS BACKGROUND OF THE INVENTION and an addition of metal vapor, such as, for example,

mercury vapor. In the event of operation of the gas discharge lamp with direct current, the metal vapor gradually shifts to the cathode (cataphoresis), so that the anode area becomes depleted in metal vapor additive after acertain time of operation, as a result of which the production of ultra violet radiation, and thus the production of light, decreases considerably along a large part of the discharge path.

The phenomenon of cataphoresis may be counteracted by reversing the polarity of the gas discharge lamp after a certain time of operation. However, this calls for a considerable expenditureand for additional servicing. i

It has also been known (DAS 1,252,801) to operate a direct current operated gas discharge lamp with comparatively high temperature to cause through thermodifiusion a return of the metal vapor into the anode area. As a result, it is possible to largely avoid the phenomenon of cataphoresis. For example, the gas discharge tube may be built up in such a manner that the hotter cathode chamber surrounds the anode chamber in order to heat the anode chamber. The radiation of heat can also be decreased through special heat insulating and light permeable covers (GM [Utility Patent] Patent) 1,707,299). In this manner, a sufficiently strong thermodiffusion can be achieved as a counter effect to cataphoresis. However, for this purpose, special constructional measures are required which are not always desirable and which also require an additional expenditure. Also, the operation of a gas discharge lamp with increased temperature is not always desired.

An object of the present invention is to create a novel electrode arrangement for do. operated gas discharge lamps, which largely compensates for the phenomenon of cataphoresis while having a simple structure. According to the invention, this is achieved through the fact that the chambers of the discharge tube which receive the electrodes lying at the end of the discharge path are connected with, one another directly by way of a gas discharge proof channel having a small cross-section. Such a connecting channel offers to the metal vapor a short path from the cathode to the anode, as a result of which the phenomenon of cataphoresis is counteracted. A direct discharge via this connecting channel will be prevented by a channel of sufficiently small cross-section but which, on the other hand, is large enough for the diffusing therethrough of the metal vapor.

Preferably, the connecting channel is developed as a capillary system or diaphragm. The electrode spaces maybe provided in the open ends of a tube element, the middle of which has been provided with a constricted place through which the connecting channel passes.

The measure according to the invention can be used for d.c. operated gas discharge lamps of any kind and of any construction.

The invention has been explained in more detail in the following paragraphs and drawing by way of an embodiment given by way of example.

THE DRAWING The drawing is a partial section in elevation taken through the'longitudinal axis of a discharge tube with the electrode arrangement shown schematically, that is to say, without the electrode tube receiving the electrode arrangement.

THE DETAILED DESCRIPTION With reference to the drawing, the numeral '10 designates generally a partof a glass tube, which preferably has been developed cylindrically."Ihis piece 10 of a glass tube'has been squeezed in the middle at point 13, so that two end parts 11 and 12 areformed with hollow spaces 16 and .17, while the constricted place 13 is passed through only by a channel l9 connecting the spaces 16 and 17 and having a comparatively slight cross-section. In the spaces 16 and 17, the

electrodes 14 and 15 have been arranged whose supply lines'20 and 21 are guided outside through the constricted place 13. The numeral 18 designates the customary pump spout. I

At the free ends 11 and 12 with the electrode spaces 16 and 17, there may follow, for example, a gas discharge tube with the desired values for itslength and diameter. At the same time, the gas discharge passes from one electrode through the gas discharge tube to the other electrode. The cross-section of the connecting channel 19 is sufficiently small to prevent a direct discharge between the electrodes 14 and 15. The connecting channel 19 is sufficiently large for the diffusing of the metal vapor therethrough so that the metal vapor, which is present to an increased degree in the area of the cathode in the case of a d.c. operated gas discharge lamp, can again reach the anode to counteract cataphoresis.

The connecting channel 19 can be developed, for example, as a capillary. It is also possible to provide a capillary system such as a diaphragm. The two electrodes 14 and 15- may be The electrode arrangement shown in the drawing can be used not only in connection with a gas discharge tube, as shown, but it can also be used in connection with othergas discharge tubes of different construction. The two electrodes 14 and 15 may be heated electrodes or cold electrodes. Thus, the invention also offers the possibility of counteracting the phenomenon of cataphoresis in cold electrode tubes.

The present invention may thus be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.

What is claimed is:

1. An electrode arrangement for a d. c. gas discharge lamp in which the spaces receiving the electrodes at the ends of the discharge path communicate by way of a first path between said electrodes within said envelopeiand,

diaphragm means for permitting the diffusion of said metallic vapor'between said electrodes along a second path, said diaphragm means preventing the establishment of a gaseous discharge along said second path.

* i k i 

1. An electrode arrangement for a d. c. gas discharge lamp in which the spaces receiving the electrodes at the ends of the discharge path communicate by way of a capillary system preventing gas discharge while simultaneously permitting the diffusion of metallic vapor therethrough.
 2. A gas discharge tube comprising: a a tight envelope containing a metallic vapor; a pair of electrodes disposed within said envelope; means for establishing a gaseous discharge along a first path between said electrodes within said envelope; and, diaphragm means for permitting the diffusion of said metallic vapor between said electrodes along a second path, said diaphragm means preventing the establishment of a gaseous discharge along said second path. 